Behavioral Neurosciences Program, McGill University, Montreal, Canada.
PLoS One. 2007 Apr 11;2(4):e369. doi: 10.1371/journal.pone.0000369.
Current theories of auditory pitch perception propose that cochlear place (spectral) and activity timing pattern (temporal) information are somehow combined within the brain to produce holistic pitch percepts, yet the neural mechanisms for integrating these two kinds of information remain obscure. To examine this process in more detail, stimuli made up of three pure tones whose components are individually resolved by the peripheral auditory system, but that nonetheless elicit a holistic, "missing fundamental" pitch percept, were played to human listeners. A technique was used to separate neural timing activity related to individual components of the tone complexes from timing activity related to an emergent feature of the complex (the envelope), and the region of the tonotopic map where information could originate from was simultaneously restricted by masking noise. Pitch percepts were mirrored to a very high degree by a simple combination of component-related and envelope-related neural responses with similar timing that originate within higher-frequency regions of the tonotopic map where stimulus components interact. These results suggest a coding scheme for holistic pitches whereby limited regions of the tonotopic map (spectral places) carrying envelope- and component-related activity with similar timing patterns selectively provide a key source of neural pitch information. A similar mechanism of integration between local and emergent object properties may contribute to holistic percepts in a variety of sensory systems.
目前的听觉音高感知理论提出,耳蜗位置(频谱)和活动时间模式(时间)信息在大脑中以某种方式结合,产生整体音高感知,然而,整合这两种信息的神经机制仍然不清楚。为了更详细地研究这个过程,向人类听众播放了由三个纯音组成的刺激,这些纯音的成分在听觉系统中是单独分辨的,但仍然会产生整体的、“缺失的基频”音高感知。该技术用于分离与音复合物的各个成分相关的神经定时活动与与复合物的突发特征(包络)相关的定时活动,并且可以来自的声拓扑图的区域同时受到掩蔽噪声的限制。音高感知与源自声拓扑图中较高频率区域的具有相似定时的与组件相关和与包络相关的神经反应的简单组合非常匹配,在该区域中,刺激成分相互作用。这些结果表明了一种整体音高的编码方案,其中携带具有相似定时模式的包络和组件相关活动的声拓扑图的有限区域选择性地提供了神经音高信息的主要来源。局部和突发对象属性之间的类似整合机制可能有助于各种感觉系统中的整体感知。